Exploring, drilling and completing hydrocarbon and other wells are generally complicated, time consuming and ultimately very expensive endeavors. In recognition of these expenses, added emphasis has been placed on efficiencies associated with well completions and maintenance over the life of the well. Over the years, ever increasing well depths and sophisticated architecture have made reductions in time and effort spent in completions and maintenance operations of even greater focus.
In terms of architecture, the terminal end of a cased well often extends into an open-hole lateral leg section. Additionally, such open-hole lateral legs are often found extending from other regions of the main vertical well bore. Such architecture may enhance access to the reservoir, for example, where the reservoir is substantially compartmentalized. Regardless, such open-hole lateral leg sections often present their own particular challenges when it comes to their completions and maintenance.
Fracturing applications, generally during well completion, constitute one area where significant amounts of time and effort are spent, particularly as increases in well depths and sophisticated architecture are encountered. Indeed, where a host of lateral legs are present as described above, a considerable amount of time and effort may be spent dedicated to fracturing of each individual leg. Once more, as described below, this expenditure of time and effort may be exacerbated by the particular sequential procedures that are required as a result of conventionally available frac equipment.
Fracturing of a lateral leg involves positioning surface fracturing equipment at the oilfield and hooking it up to the well. A frac string tubular terminating in a liner for positioning in the lateral leg may then be advanced to the leg for the fracturing application. Additionally, depending on the technique for directing the liner to the leg, a deflector may be pre-positioned in the main bore of the well for such guidance. Further, once the fracturing application takes place through the liner, the frac string tubular may be removed and the well tested, with focus on flow of the fractured lateral leg. Subsequently, the surface fracturing equipment may be reset, the frac string tubular outfitted with another frac liner, and the process repeated at another lateral leg.
Overall, each leg of a multilateral well may be effectively fractured according to techniques such as those described above. However, the amount of time and effort spent on setting and re-setting surface fracturing equipment is quite significant. For example, once the initial fracturing takes place in the first lateral leg, subsequent testing, potential clean-out and other treatment of the leg closely follows. This requires the removal and replacement of the large fracturing equipment coupled to the well at the oilfield surface. Additionally, with the follow-on testing and potential treatment of the lined lateral leg, it is unlikely that a subsequent fracturing of another leg will take place in less than a few weeks.
It is not uncommon for the architecture of today's multilateral wells to include five or more lateral legs branching from the main bore. According to techniques described above, for each leg to be fractured, this would include positioning a deflector downhole, setting massive fracturing equipment, running a fracturing application, removing fracturing equipment and testing and/or treating the well and leg. Even this leaves out fracturing of the main bore and assumes that each lateral leg is pre-drilled before fracturing is begun, which generally is not going to be the case. Thus, as a practical matter, complete fracturing of a multi-lateral well is likely to take several months as well as countless man hours in numerous rig-ups and replacements of surface fracturing equipment.